Electrical ignition systems are used in most automotive vehicles to create a high-voltage current (about 20,000 to about 40,000 volts or more) to a sparkplug and create an arc across the gap at the base of the sparkplug. This high-voltage current creates a strong spark that ignites the air/fuel mixture for combustion. The ignition system also controls the spark timing such that the spark occurs at the right time and in the correct cylinder. Although many different automotive ignition systems have developed over the last century, most ignition systems only differ in the method or system used to create the spark.
In the original electrical ignition systems, a mechanical system used simple breaker points as a switching mechanism to control a current flow through an ignition coil containing the primary and secondary winding circuits. Usually the primary winding of the ignition coil contains about 100 to about 150 turns of heavy and insulated copper wire. The insulation insulates the turns and prevents electrical shorts. A secondary coil winding contains about 15,000 to about 30,000 or more turns of fine copper wire, also insulated, and typically wound around a soft iron core. Usually oil is used for cooling the coil and it provides a medium to protect the coil from the excessive heat generated by large current flows. Other cooling mechanisms can also be used. As current flows through the primary coil, a magnetic field is established. When the breaker points are opened, the current is shut off and the collapsing magnetic field induces a high voltage in the secondary winding that is released through a center coil tower to a rotor, which distributes spark through a distributor cap and high tension sparkplug wires to the proper sparkplug.
Automotive electrical ignition systems have advanced over the years from simple vacuum advance mechanical systems to electronic systems. Modern ignition systems use distributorless (electronic) ignition systems (EIS) that replace prior mechanical and simple electronic ignition systems with computer-controlled spark advance. In a distributorless ignition system (DIS), a crankshaft timing sensor triggers the ignition system, which typically includes a Hall Effect magnetic switch activated by vanes on a crankshaft damper and pulley assembly. A signal is generated corresponding to vehicle engine timing and RPM and transmitted to the distributorless ignition system (DIS) and a microprocessor that is part of a distributorless ignition system (DIS) electronic control assembly or module. A camshaft sensor can provide information on cylinder position for the ignition coil and fuel system. The distributorless ignition system (DIS) electronic engine assembly receives a signal from the crankshaft sensor and camshaft sensor and a spark signal from a computer of the vehicle to control the ignition coils, allowing them to fire in the correct sequence. The DIS electronic control assembly can also control engine dwell. An ignition coil pack can use multiple ignition coils and the DIS electronic control assembly controls the coils.
The DIS ignition system and similar circuit components are commonly used on most modern automotive vehicles. Millions of earlier designed electronic ignition systems (EIS), however, are still used on earlier vehicle models and are still operable, although many are now failing. These earlier electronic ignition systems still use a computer-controlled spark advance system and ignition coil having the primary and secondary windings. An electronic control assembly (ECA) receives many sensor inputs and generates a spark output (SPOUT) signal. The distributor has a typical multipoint or similarly designed rotor or armature, shaft assembly and a Hall Effect stator assembly mounted in the distributor that generates a profile ignition pickup (PIP) signal to the electronic control assembly (ECA) indicative of crankshaft position and engine RPM. An ignition module is formed as a thick film integrated (TFI) module and has an integrated circuit within a module housing that is usually mounted on the distributor base. It receives the spark output (SPOUT) signal from the electronic control assembly (ECA). The TFI module generates a control signal to the ignition coil and switches ON and OFF the primary current therein, typically using an insulated gate field effect transistor (IGFET) or similar switching device.
A major drawback of these prior art thick film integrated (TFI) modules and similar ignition modules is the excessive production of generated heat resulting from the large duty cycle and constant ON operation when the TFI module generates signals to the ignition coil to fire the spark at proper timing intervals. Although the TFI module usually includes a heat sink to aid in absorbing excessive amounts of generated heat at low idle speeds and other automotive operations conditions, excessive heat is still generated, at the TFI module and ignition coil, possibly resulting in logic errors, signal transmission errors, and other automotive problems.